Method and apparatus for determining a composition characteristic of a combustible fluid

ABSTRACT

METHOD AND APPARATUS FOR CONTINUOUSLY DETERMINING A COMPOSITION CHARACTERISTIC OF A COMBUSTIBLE FLUID, SUCH AS THE OCTANE RATING OF A GASOLINE BOILING RANGE HYDROCARBON-CONTAINING FLUID. A SAMPLE OF THE FLUID IS OXIDIZED IN AN ANALYZER COMPRISING A STABILIZED COOL FLAME GENERATOR WITH A SERVO-POSITIONED FLAME FRONT. THE POSITION OF THE FLAME FRONT IS AUTOMATICALLY DETECTED AND UTILIZED TO MANIPULATE A COMBUSTION PARAMETER, SUCH AS PRESSURE, TEMPERATURE, FLUID FLOW, OR OXIDIZER FLOW, IN A MANNER SUFFICIENT TO IMMOBILIZE THE FLAME FRONT REGARDLESS OF FLUCTUATIONS IN COMPOSITION CHARACTERISTIC OF THE FLUID SAMPLE. CHANGES IN COMBUSTION PARAMETER WHICH ARE REQUIRED TO IMMOBILIZE THE FLAME FRONT ARE CORRELATABLE WITH CHANGES IN COMPOSITION CHARACTERISTIC, AND MEANS IS PROVIDED FOR SENDING THE MANIPULATED COMBUSTION PARAMETER AND DEVELOPING THEREFROM A CONDITION OUTPUT SIGNAL WHICH IS FUNCTIONALLY REPRESENTATIVE OF AND CORRELATABLE WITH COMPOSITION CHARACTERISTIC. A SUITABLE REFERENCE FUEL OF KNOWN COMPOSITION CHARACTERISTIC IS PERIODICALLY PASSED TO THE ANALYZER IN PLACE OF THE FLUID SAMPLE AND AN ANALYZER TEMPERATURE IS SENSED. MEANS IS PROVIDED TO COMPENSATE THE CONDITION OUTPUT SIGNAL FOR ANY DEVIATION IN THE   SIGNAL BETWEEN APPARENT REFERENCE FUEL SIGNAL AND A SIGNAL CORRESPONDING TO THE TRUE KNOW VALUE OF REFERENCE FUEL COMPOSITION CHARACTERISTIC, AND TO FURTHER COMPENSATE THE CONDITION OUTPUT SIGNAL FOR TEMPERATURE FLUCTUATIONS, WHEREBY THE CONDITION OUTPUT SIGNAL IS COMPENSATED FOR COMBUSTION EFFECTS NOT INDICATIVE OF COMPOSITION CHARACTERISTIC, AND IS THEREBY FUNCTIONALLY REPRESENTATIVE OF AND CORRELATABLE WITH THE TRUE COMPOSITION CHARACTERISTIC OF THE FLUID SAMPLE.

United States Patent y 3,582,280 METHOD AND APPARATUS FOR DETERMINING ACOMPOSITION 'CHARACTERISTIC OF A COM- BUSTIBLE FLUID Ellsworth R.Fenske, Palatine, Ill., assignor to Universal Oil Products Company, DesPlaines, Ill. Continuation-in-part of application Ser. No. 679,328, Oct.31, 1967. This application May 15, 1970, Ser. No. 37,639

Int. Cl. F23n 5/00; G01n 25/46, .33/2225 U.S. Cl. 23-230 laims ABSTRACTOF THE DISCLOSURE required to immobilize the flame front arecorrelatable with changes in composition characteristic, and means isprovided for sensing the manipulated combustion parameter and developingtherefrom :a condition output signal which is functionallyrepresentative of and correlatable with composition characteristic. Asuitable reference fuel of known composition characteristic isperiodically passed to the analyzer in place of the liuid sample and 1ananalyzer temperature is sensed. Means is provided to compensate thecondition output signal for any deviation in the signal between apparentreference fuel signal and a signal corresponding to t-he true knownValue of reference fuel composition characteristic, and to furthercompensate the condition output signal for temperature fluctuations,whereby the condition output signal is compensated for combustion electsnot indicative of composition characteristic, and is therebyfunctionally representative of and correlatable with the truecomposition characteristic of the fluid sample.

CROSS-REFERENCE TO RELATED APPLICATION This application is acontinuation-in-part application of co-pending application Ser. No.679,328 liled on Oct. 31, 1967, now U.S. Pat. No. 3,533,746.

BACKGROUND OF THE INVENTION The present invention relates to a methodand apparatus for determining a composition characteristic of acombustible uid. It further relates to an improvement in the method andapparatus for determining a composition characteristic of a combustibleuid utilizing a stabilized cool ame generator with a servo-positionedame front. It particularly relates to an improvement in the method andapparatus for determining a composition characteristic of a hydrocarboncomposition. It more specifically relates to an improved method andapparatus for determining the octane number of a gasoline boiling rangehydrocarbon fluid.

Those skilled in the art are familiar wth the phenomenon of cool amegeneration. Briey, when a mixture of hydrocarbon vapor and oxygen at acomposition within the explosion limit is held at conditions of pressureand temperature below the normal ignition point, partial oxidationreactions occur which generally result in the formaice tion ofby-products, such as aldehydes, carbon monoxide, and other partiallyoxidized combustion products. These products are apparently produced viaa chain reaction which, it is believed, also produces ions which then insome manner continue the reaction chain. If such a mixture ofhydrocarbon vapor and oxygen is isolated and compressed and/or heated sothat these chain reactions proceed at significant reaction rates, thencool flames are observed within the chamber. The cool ames arecharacterized as light emissions accompanied by the evolution ofrelatively minor amounts of heat.

Implicit in this definition is the fact that the phenomenon of cool amegeneration is short of total combustion and short of total ignition andexplosion. The work of Barusch and Payne in Industrial and EngineeringChemistry, Volume 43, pages 2329-2332, 1951, describes in detail theresults which can be obtained from continuous or stabilized cool flames.

Basically, the utilization of this phenomenon in the practice of thepresent invention is one of manipulating a combustion parameter in amanner suicient to immobilize the cool ame relative to one end of thecombustion chamber. The manipulated combustion parameter is sensed andutilized to develop a condition output signal which is functionallyrepresentative of and correlatable with the composition of the liuidbeing oxidized in the combustion chamber.

A more complete explanation and description of the basic apparatus andbasic method for detecting composition characteristics utilizing coolflames is contained in U.S. Pat. 3,463,613, issued on Aug. 26, 1969, toE. R. Fenske and J. H. McLaughlin. The contents of said patent areincorporated herein by reference so that a greater detailed discussionneed not be presented in this application. Those skilled in the art arereferred directly to the entire teaching contained in said patent foradditional and specific details as to the construction of a preferredembodiment of the basic apparatus and method of operation thereof. Aswill be more fully developed hereinafter, the present inventiondescribes and claims an improvement in the basic method and apparatusdisclosed and claimed in said patent.

One of the difliculties encountered in the method and apparatusdisclosed in U.S. Pat. 3,463,613 is concerned with calibration of theapparatus to compensate for combustion effects which are not indicativeof composition characteristics of the fluid being analyzed.

For example, it has been found that when the apparatus disclosed in theU.S. Pat. 3,463,613 has been operated on a combustible iiuid for asubstantial length of time, the apparatus occasionally begins to producecondition output signals which reect aging of the apparatus. This agingmay be introduced due to plugging of preheaters or plugging of a owdilfusor element which is mounted in the interior of the combustionchamber a short distance above the combustion nozzle. Additionally, ithas been found that Where a leaded gasoline is the combustile fluidbeing analyzed, deposits of lead oxides within the combustion chamberintroduce combustion effects which are not indicative of the compositioncharacteristic of the gasoline fraction being burned within the chamber.

It has further been discovered that lluctuations in the oxidizer passinginto the combustion chamber will introduce combustion effects which willresult in a condition output signal containing an error which is notcorrelatable with the composition characteristics of the fluid beingburned within the chamber. For example, the typical oxidizer passinginto the combustion chamber is derived from a compressed air system, andthe compressed air will contain microscopic yquantities of entrainedlubricating oil which have been picked up at the air compressor.

Additionally, it has been found upon occasion that a shift in the winddirection will introduce llue gas from nearby furnace stacks so that theair compressor is periodically picking up air containing combustionproducts. This results in an oxidizer passing into the combustionchamber of the instant analyzer which is not only deficient in oxygen,but which also may contain a considerable proportion of furthercombustible material such as carbon monoxide and unburned hydrocarbonscontained in the flue gas.

Furthermore, it is typical in the art to place the combustion analyzerof the instant invention in a local mounting near the product streamwhich is to be analyzed, and to transmit condition output signalstherefrom to the control house in the refinery or chemical plant whereinthe apparatus is utilized for monitoring or controlling service.Consequently, the combustion chamber of the apparatus is locatedout-of-doors and is subject to thermal fluctuations due to atmosphericconditions. These lluctuations in atmospheric conditions produce thermaleffects within the combustion chamber which are not indicative of thecomposition characteristic of the fluid being analyzed therein.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide an improved method and apparatus for analyzing acombustible lluid.

It is another object of the present invention to provide an improvedmethod and apparatus for analyzing a combustible lluid in a stabilizedcool llame generator.

It is still another object of the present invention to provide a methodand apparatus for determining a composition characteristic of ahydrocarbon composition.

It is a still further object of the present invention to provide animproved method and apparatus for determining the octane rating of agasoline boiling range hydrocarbon fluid.

Therefore, in its method aspects, a broad embodiment of the presentinvention provides a method for detecting composition characteristic ofa combustible fluid which comprises: (a) introducing a sample stream ofsaid lluid and a stream of oxygen-containing gas into one end of Iacombustion zone including an induction section maintained at elevatedtemperature; (b) partially oxidizing said sample stream in saidcombustion zone under conditions sufficient to generate and maintaintherein, a cool llame characterized by a relatively narrow well-definedflame front spaced from said one end; (c) sensing the position of saidllame front relative to said one end, and developing therefrom a controlsignal; (d) utilizing said control signal to adjust a combustionparameter selected from the group consisting of combustion zonepressure, induction section temperature, sample stream flow rate, andoxygencontaining gas stream flow rate, in a manner sufficient toimmobilize said flame front relative to said one end regardless offluctuations in the composition characteristic of said sample stream;(e) sensing the adjusted parameter and passing a first parameter signalinto signal conditioning means; (f) manipulating said first parametersignal in said signal conditioning means and therefrom producing a rstcondition output signal functionally representative of the apparentcomposition characteristic of said fluid sample stream, and functionallyresponsive to changes in composition characteristic of said samplestream; (g) periodically isolating said sample stream from saidcombustion zone, and simultaneously passing a stream of reference fuelhaving a known value of composition characteristic, into said zone in amanner sufficient to continue the generation of said immobilized llamefront; (h) sensing the adjusted parametes during the period of isolationand passing a second parameter signal into said signal conditioningmeans, said second parameter signal being functionally representative ofthe apparent composition. characteristic of said reference fuel; (i)comparing said second parameter signal with a reference value ofparameter signal functionally corresponding to the actual known value ofcomposition characteristic of said reference fuel; (j) adjusting saidsignal conditioning means in a manner sufficient to produce a secondcondition output signal which is compensated to reflect the eliminationof the difference between said second parameter signal and saidreference value parameter signal,

and which is thereby functionally representative of the actual knowncomposition characteristic of said reference fuel; and, (k) periodicallyisolating said reference fuel stream from said combustion zone whileretaining the sign-al conditioning adjustment of step (j), andsimultaneously passing said fluid sample stream into said zone in amanner sufficient to maintain said llame front, whereby said signalconditioning means receives a third parameter signal and therefromdevelops a third condition output signal compensated for combustioneffects not indicative of composition characteristic, and said thirdcondition output signal is thereby functionally representative of theactual composition characteristic of said sample stream.

Furthermore, in its method aspects, an additional broad embodiment ofthe present invention provides a method for detecting compositioncharacteristic of a combustible fluid which comprises: (a) introducing asample stream of said fluid and a stream of oxygen-containing gas intoone end of a combustion zone encompassed by a zone of elevatedtemperature, said combustion zone including an induction sectionmaintained at elevated temperatures; (b) partially oxidizing said samplestream in said combustion zone under conditions suflicient to generateand maintain therein, a cool llame characterized by a relatively narrowwell-delined flame lfront spaced from said one end; (c) sensing theposition of said llame front relative to said one end, and developingtherefrom a control signal; (d) utilizing said control signal to adjusta combustion parameter selected from the group consisting of combustionzone pressure, induction section temperature, sample stream llow rate,and oxygen-containing gas stream flow rate, in a manner suilicient toimmobilize said llame Kfront relative to said one end regardless offluctuations in the composition characteristic of said sample stream;(e) sensing the adjusted parameter and developing a parameter signalresponsive to changes in said composition characteristic; (f) sensing atemperature selected from the group consisting of induction sectiontemperature and a temperature of said elevated temperature zone, anddeveloping a temperature signal responsive to fluctuations in sensedtemperature; (g) passing said parameter signal and said temperaturesignal into signal conditioning means, and producing therefrom acondition output signal functionally representative of the compositioncharacteristic of said lluid sample stream, said condition output signalbeing indicative of said composition characteristic as corrected -forfluctuations in sensed temperature.

In addition, in its apparatus aspects, a broad embodiment of the presentinvention provides a composition analyzer for detecting a compositioncharacteristic of a combustible chemical fluid which comprises incombination: (a) a combustion chamber, including an induction section;(b) means for generating within said combustion chamber, a cool flamecharacterized by a relatively narrow well-defined llame front, utilizingas fuel therefor said combustible chemical uid to be analyzed, saidgenerating means including means passing a stream of said fluid and astream of oxidizer into said combustion chamber; (c) means sensing thephysical position of said flame front within said combustion chamber;(d) control means coupled to said position sensing means, and adapted toadjust a combustion parameter selected from the group consisting ofcombustion pressure, induction section temperature, lluid stream flowrate, and oxidizer stream flow rate, in a manner suicient to immobilizesaid tlame front in a constant physical position relative to saidcombustion chamber; (e) means sensing the adjusted parameter anddeveloping a parameter output signal which is functionallyrepresentative of the composition characteristic of said fluid stream;(f) signal conditioning means receiving said parameter output signal;(g) condition signal generating means Within said signal conditioningmeans producing a condition output signal representative of saidcomposition characteristic; (h) means periodically isolating said fluidstream from said llame generating means, and for simultaneously passinga stream of reference fuel having a known value of compositioncharacteristic, into said flame generating means in a manner sufficientto continue the generation of said immobilized llame front; (i) meanspassing to said signal conditioning means, a timing signal indicative ofthe passage of reference fuel to said flame generating means; (j)comparison meanse within said signal conditioning means, responsive tosaid timing signal, adapted to compare the condition output signalgenerated due to reference -fuel flame front `with a reference valuesignal functionally corresponding to the actual known value ofcomposition characteristic of said reference fuel, and developingtherefrom a comparison signal; (k) adjusting means within said signalconditioning means responsive to said comparison signal, and adapted toadjust said condition signal generating means to compensate fordeviation between the condition output signal generated due to referencefuel llame front and said reference value signal; and (l) means forretaining said adjustment to said condition signal generating means whensaid isolation period is ended and said fluid stream is returned to saidflame generating means in place of said reference fuel, whereby thecondition output signal generated by said fluid stream flame front iscompensated for combustion effects not indicative of compositioncharacteristic, and said condition output signal is thereby functionallyrepresentative of and correlatable with the actual compositioncharacteristic of said combustible chemical fluid.

Still further, in its apparatus aspect, a broad embodiment of thepresent invention provides a composition analyzer for detecting acomposition characteristic of a combustible chemical fluid whichcomprises in combination: (a) a combustion chamber encompassed by anouter chamber confining a zone of elevated temperature thereinbetween,said combustion chamber including an induction section maintained atelevated temperature; (b) means for generating within said combustionchamber, a cool flame characterized by a relatively narrow welldefinedflame front, utilizing as fuel therefor said combustible chemical fluidto be analyzed, said generating means including means passing a streamof said fluid and a stream of oxidizer into said combustion chamber; (c)means sensing the physical position of said flame front within saidcombustion chamber; (d) control means coupled to said position sensingmeans, and adapted to adjust a combustion parameter selected from thegroup consisting of combustion pressure induction section temperature,fluid stream flow rate, and oxidizer stream flow rate in a mannersullicient to immobilize said flame front in a constant physicalposition relative to said combustion chamber; (e) means sensing theadjusted parameter and developing a parameter output signal which isfunctionally representative of the composition characteristic of saidfluid stream; (f) means sensing a temperature selected from the groupconsisting of a temperature within said induction section and atemperature of said confined elevated temperature zone, and developing aternperature signal responsive to fluctuations in sensed temperature;and (g) signal conditioning means receiving said parameter-output signaland said sensed temperature signal, and producing therefrom a conditionoutput signal which is functionally representative of and correlatablewith said composition characteristic of the combustible chemical fluid,said condition output signal being indicative of said compositioncharacteristic as corrected for fluctuations in sensed temperature.

In essence, therefore, the present invention provides a method andapparatus which determines the composition characteristic of acombustible fluid by oxidizing the fluid in a stabilized cool flamegenerator with a servopositioned flame front, to develop a conditionoutput signal which is temperature compensated, and which isperiodically recalibrated to compensate for deviations in conditionoutput signal generated by a reference fuel of known compositioncharacteristic. In this manner then, the condition output signal iscontinuously compensated for combustion effects which are not indicativeof composition characteristic, and the condition output signal isthereby rendered functionally representative of and correlatable withthe true composition characteristic of the combustible fluid beinganalyzed.

As used herein, the term composition characteristic does not refer to acompound by compound analysis of the type presented by instruments suchas mass spectrometers or vapor phase chromatographs. Rather, thecomposition characteristic is represented by a continuous, orsubstantially continuous, output signal which is responsive to andindicative of the fluid composition, and which is more specifically,empirically correlatable with one or more conventional compositionidentifications or specifications. For example, when the fluid to beanalyzed is a hydrocarbon composition, the composition characteristicwhich is represented by the condition output signal may be aconventional identification or specification such as the Reid VaporPressure, ASTM or Engler distillation, initial boiling point, endboiling point, etc. In particular, when the fluid being analyzedcomprises gasoline boiling range hydrocarbon, the compositioncharacteristic which is functionally represented by the condition outputsignal will typically comprise a knock characteristic such as researchoctane number or motor octane number.

The specific nature of the correlation between the condition outputsignal and the actual Value of composition characteristic is a functionof the actual composition of the fluid being analyzed. Where the fluidbeing analyzed comprises a hydrocarbon, the correlation between thecondition output signal and the composition characteristic will be afunction of the hydrocarbon fluid composition and the carbon number ofthe hydrocarbon constituents present therein. Furthermore, thecorrelation is further influenced by the presence or absence ofparafiins, isoparaflins, olelins, diolefins, polyolens, aromatics,long-chain substituted aromatics, polynuclear aromatics, etc. Thus aspresently operated in commercial practice, the apparatus of the presentinvention is capable of continuously Calibrating itself for a particularhydrocarbon blend or charge stock and relatively small deviations due tofluctuations in molecular species can be accounted for.

However, as noted hereinabove, the apparatus of the present inventionmust be continuously recalibrated and compensated for combustion effectswhich are not indicative of the composition of the fluid being analyzedor of the composition characteristic being developed as the conditionoutput signal. In order to achieve this compensation in the conditionoutput signal, there is provided means for periodically isolating thefluid being tested from the combustion chamber of the apparatus, and forsimultaneously introducing therein a sample of reference fuel. Thoseskilled in the art are familiar with the procedures for obtainingreference fuels of known composition. Since the reference fuel is beingcompared to the unknown fluid, it is particularly desirable that thehydrocarbon species of the reference fuel be similar to those of theunknown fluid being tested. Thus for example, if the fluid beinganalyzed is a hydrocarbon comprising a gasoline fraction having anoctane number of about and consisting primarily of a reformate gasoline,it is particularly desirable that the reference fuel also be a reformategasoline having an octane number of about 95.

Under such conditions then, the condition output signal generated by thecombustion of the reference fuel will be indicative of the detectedcomposition characteristic of the reference fuel and provide a validbasis for comparison to the sample of unknown fuel being tested.Therefore, any deviation of the co-ndition output signal of thereference fuel from the known condition output signal corresponding tothe known composition characteristic of the reference fuel will be adeviation in the system which is due to combustion effects which are notindicative of the composition characteristic. Accordingly, then, theapparatus of the present invention will make a corrective adjustment inthe condition output signal to produce a signal which is trulyrepresentative of the actual composition characteristic of the referencefuel. Therefore, when the unknown sample is again introduced into thecombustion chamber, the condition output signal thereby generated willhave been compensated and corrected for the deviations found in thetesting of the apparatus with reference fuel.

As used herein, the terms output signal, and condition output signal areto be construed in their most meaningful sense and include analogsignals of all types, such as amplitude-modulated, phase-modulated, orfrequencymodulated electrical signals or pressure signals byconventional pneumatic transmission media, as well as digitalrepresentations thereof. These terms are further intended to includesimple mechanical motion or displacement of a transducer member (whetheror not mechanically, electrically, or pneumatically coupled to aphysical display means, such as an indicating arm, recorder pin, ordigital display board) including by way of illustration, the expansionor contraction of a Bourdon tube, pressure spiral or helix, thedisplacement of a bellows-dapper, nozzlediaphragm, or differentialtransformer-core assembly, the movement of a bimetallic temperatureresponsive element, the motion of a slider of a self-balancingpotentiometer, etc.

The condition output signal may be transmitted without physical displaydirectly to reset a final control unit, such as a diaphragm motor Valveor a sub-control loop in a cascade system. More commonly, however, thecondition output signal will pass to a readout device which willcomprise or will be coupled to an indicating or recording means, thescale or chart of which may be calibrated in terms of the desiredidentifying composition characteristic of the iiuid sample, such asoctane number, initial boiling point, 90% boiling point, vapor pressure,and the like.

In the practice of this invention, the location of the cool ame frontis, preferably, determined by temperature sensing devices, such as apair of axially spaced thermocouples fixed at a known distance from oneend of the combustion zone and at a known and lixed distance from eachother, eg. one (l) inch. As will be more fully developed hereinbelow,the signal developed by the thermocouple means activate appropriatecontrol means for adjusting a combustion zone parameter or condition soas to immobilize the cool flame front at a position generally betweenthe two spaced thermocouples. A most satisfactory combustion conditionwhich can be used as the control means is the combustion zone pressure.

Test samples which can be continuously analyzed by this inventioninclude normally gaseous and normally liquid combustible chemicals. In aparticularly preferred embodiment, the test samples comprisehydrocarbon-containing mixtures. These mixtures typically comprise atleast one hydrocarbon containing from l to about 22 carbon atoms permolecule in admixture with one or more non-hydrocarbons such ashydrogen, nitrogen, carbon monoxide, carbon dioxide, water, and hydrogensulfide. Alternatively, these mixtures will comprise at least twodifferent hydrocarbons containing from 1 to about 22 car- 8 bon atomsper molecule. The upper limit on carbon number is Iixed generally by thepreferred operational procedure whereby the test sample and thereference fuel sample are vaporized in an air stream under combustionconditions without undergoing any substantial thermal decompositionprior to the oxidation thereof.

Therefore, in the context of the present invention, the termscombustible chemical fluid and combustible fluid are intended to embodyall forms of combustible fluids which are capable of vaporization withinthe apparatus, and particularly hydrocarbon mixtures in whichhydrocarbons predominate, but which may also contain significant amountsof non-hydrocarbon materials. In particular, the hydrocarbon fluids maycontain such items as tetraethyl lead, tetramethyl lead, and other knownantiknock compounds for use in motor fuel compositions. In the preferredand practical embodiment of this invention, wherein the determinedcomposition characteristic is the measurement of octane rating, thefeedstocks or test samples of unknown octane number which are chargeableto the apparatus of the present invention include those within thegasoline boiling range including such process streams as straight-rungasoline, cracked gasoline, motor alkylate, catalytically reformedgasoline, thermally reformed gasoline, hydrocracker gasoline, etc.

The oxidizer or oxidizing agent utilized in the apparatus of the presentinvention is preferably an oxygen-containing gas, such as air,substantially pure oxygen, etc. or it may be a synthetic blend of oxygenwith an inert or equilibrium effecting diluent, such as nitrogen, carbondioxide or steam.

The generation of the stabilized cool tiame is effected under combustionconditions generally including superatmospheric pressure and elevatedtemperature, although in some cases, it may be desirable to useatmospheric pressure or sub-atmospheric pressure. For example, thepressure may be in the range from about 15 p.s.i.a. to about p.s.i.a.with a maximum flame front temperature in the range of 600 F. to 1000 F.For measuring the composition of a gasoline boiling range fraction it ispreferable to employ pressures in the range from 16 p.s.i.a. to 65p.s.i.a., more preferably, in the range from 16 p.s.i.a. to 30 p.s.i.a.,together with an induction zone temperature of from about 550 F. toabout 850 F. Control of induction zone temperature can be effected bythe amount of preheat imparted to the air or oxidizer stream and to theincoming sample stream, including the test sample and the referencesample. Furthermore, induction zone temperature may be manipulated rbyadjusting the input of heat from an external source to the combustionzone proper. In any case, the permissible limits Within whichtemperature and pressure may be individually varied without departurefrom stable operation, even outside of the specific operational limitsreferred to herein, can be determined by simple experiment for aparticular type and quantity of combustible fluid sample.

As previously mentioned, the detection of the position within thecombustion chamber for the test sample and for the reference sample ispreferably effected by temperature responsive thermoelectrical means,although other equivalent means can be used. The thermocouple sensingdevice may be placed within the combustion chambers, as discussedhereinabove, or outside of the combustion chamber, and may be eitherfixed or may be movable in such a manner as to completely andsubstantially traverse the length-wise direction of the combusitionchamber in order to locate the position of the stabilized cool flamewithin the combustion chamber.

The output signal from the thermocouple sensing means is fed throughsignal means to suitable control means such as a motor activated controlvalve for regulating, preferably, the pressure within the combustionzone. Generally, the output signal from the thermocouple sensing meansis not lead to a readout device, such as a strip chart or x-y recorder,for to do so would deplete the strength of the signal to such an extentthat operational efficiency might be impaired. Preferably, thethermocouple sensing device comprises a pair of axially spacedthermocouple leads which are inserted into thin-walled thermal typepencil wells and may be constructed of any materials known to thoseskilled in the art, such as for example, iron-constantan. The lead wiresfrom the thermowells are connected to a suitable differentialtemperature controller. Such controller may be a conventionalself-balancing potentiometer in combination with pneumatic controlmeans. A suitable input span for the controller may be from H to +5millivolts and the output signal thereof transmitted may be aconventional 3-15 p.s.i.a. air signal. This control signal is used, forexample, to reset the set point on a back pressure controller or can beused to directly control the pressure within the combustion zone.

The present invention may be more fully understood by now referring tothe accompanying drawings.

fFIG. 1 comprises a simplified schematic representation of the apparatusfor practicing the present invention wherein the signal conditioningmean is a computer means, which may be an analog computer or a digitalcomputer.

FIG. 2 illustrates a schematic representation of the apparatus forpracticing the present invention wherein the signal conditioning meanscomprises an analog or a digital network.

DESCRIPTION KOl?" THE lDRAWINGS With reference now to the accompanyingFIG. 1, there is shown the apparatus of the present invention whichcomprises in combination a canister 1 enclosing a combustion chamber 2.The canister has means for introducing a heat transfer fluid to surroundthe combustion chamber so that proper temperature conditions may bemaintained within the combustion zone, by controlling temperature in anelevated temperature zone 3 which is confined between the canister 1 andthe combustion chamber 2. The conguration of the apparatus will besimilar to that described in the cited U.S. Pat. 3,463,613. Thus thetemperature within the elevated temperature zone 3 may be maintained bya constant circulation of a heat transfer fluid from an external source,or by conduction and natural convection of the heat transfer fluid asprovided by immersion heaters contained within the canister and withinthe zone 3, or heating elements encompassing the canister. If desired,the exterior of the enclosing canister 1 may be encased in one or morelayers of insulation, not shown, and typically this will be done sincethe canister is normally located out-ofdoors and exposed to atmosphericconditions. Those skilled in the art being familiar with the teachingspresented herein and with the teachings presented in the cited patentwill understand the appropriate manner of enclosing the cornbustionchamber in a suitable canister having appropriate temperature controlmeans and having appropriate thermal insulation in order to minimize thethermal effects of atmospheric conditions.

With reference to the combustion chamber 2, there is providedtemperature sensing means 4 and 5 which are capable of sensing thelocation of the stabilized cool llame front generated within thecombustion chamber by the oxidation of the sample being introducedtherein. The combustion chamber 2 is provided with inlet means 6 whlchintroduces a mixture of air, or other oxidizing agent, and a combustiblefuel into a burner nozzle, not shown, contained within the lower sectionof the combustn chamber 2. The air or oxidizing agent is introduced intothe system via line 8 and the combustible fluid is introduced into thesystem via line 7. The net combustion products are ultimately dischargedfrom the combustion chamber via line 9.

The mixture of air and combustible fluid passes into the chamber 2 vialine 6 wherein it is ignited due to the elevated temperature. The regionof the combustion charnber 2 which is located between the inlet line 6and the temperature sensing means S is known as the induction section.The induction section is defined as that portion of the combustion zonewherein oxidation of the combustible fluid is initiated. Therefore theinduction section more particularly comprises that portion of thecombustion chamber 2 located between the burner nozzle and the coolflame front which is generated by the combustion.

In a preferred embodiment of the present invention the apparatus shownin the attached FIG. l is utilized to detect the octane number of agasoline fraction of unknown composition. The gasoline fraction isintroduced into the system via line 19 and control means 21, and thefraction enters line 7 wherein it is contacted with a stream of airpassing into the system via line 8. The air and the gasoline fractionpass into the combustion chamber 2 via line 6. The mixture of air andgasoline passes through the burner nozzle at the bottom of chamber 2,not shown, and enters the induction section of the combustion chamber.The temperature of the induction section is about 630 F. and ismaintained thereat by the heated fluid medium which completely surroundsthe combustion chamber in the elevated temperature zone 3. The oxygenand the gasoline react within the induction section producing anexothermic reaction resulting nally in a temperature elevation to a peakof about 750 F., whereat there is developed a cool flame front. At thispoint, the temperature of the combustion mixture falls off rapidly toabout 640 F. When the cool ame front is stabilized, the temperaturesensing means 4 and 5 will sense an identical temperature due to thefact that the combustion produces a peak temperature with a rapidtailing off of temperature. The exhaust gases from the combustion thenleave the combustion chamber 2 via line 9.

With reference to the combustion parameter which is manipulated andadjusted in order to stabilize or immobilize the cool flame frontbetween temperature sensing means 4 and 5, the preferred embodiment isto adjust the pressure within the combustion zone, as was previouslymentioned hereinabove. In other words, an increase in pressure willcause the flame front to recede towards the burner end of combustionchamber and a decrease in pressure will cause the flame front to advanceaway from the burner end of the chamber and more closely approach thedischarge end thereof. Therefore, if the flame front attempts to movetoward the burner end of the chamber, the temperature sensing 'means 5will reect a temperature rise. Temperature sensing means 4 and 5 willtransmit the sensed temperatures via transmitting means 10 and 11 to adifferential temperature controller 12, which will then activate apressure controller 14 by passing a pressure control signal thereto vialine 13. The pressure controller will be activated in order to decreasecombustion pressure until the flame front is restored to its originalposition between the axially spaced temperature sensing means 4 and 5.Conversely, if the hydrocarbon composition changes so that the flamefront attempts to move away from the burner end of the chamber,temperature sensing element 4 will sense a temperature rise and thedifferential temperature controller will activate the pressurecontroller 14 to increase combustion chamber pressure until the front isrestored to the original position.

Although the preferred embodiment of the invention comprises themanipulation of pressure as the controlled combustion parameter, othercombustion conditions may be adjusted, with equally satisfactoryresults, in a manner sufficient to immobilize the flame front to aconstant position within the combustion chamber. Thus, as disclosed inthe cited U.S. Pat. 3,463,613, a combustion parameter which may beadjusted by the control signal 13 from the differential temperaturecontroller 12 includes the hydrocarbon sample flow rate in line 7, theoxygen containing gas flow rate in line 8, and the induction zonetemperature. In either case, regardless of which combustion conditionparameter is manipulated, the apparatus operates with the selectedcombustion parameter being adjusted in a manner to immobilize the flamefront relative to its position within the combustion chamber 2,regardless of changes in the test sample composition. Thus thecombustion parameter is sensed and utilized to develop an output signalwhich is then indicative of the composition characteristic of thecombustible fluid being analyzed, which in a preferred embodiment is theoctane number of a gasoline sample.

The temperature sensing means for determining the location of thestabilized cool flame is preferably a thermal-electric means such as apair of axially spaced thermocouples 4 and 5. However, other means fordetermining the flame position will be apparent to those skilled in thecontrol arts and are deemed embraced in the broad scope of thisinvention. For example, one may employ spaced resistance bulbs or`simply a pair of spaced resistance wires stretched tightly across thecombustion zone, connected in a standard bridge circuit, instead of thepreviously described thermalelectric elements. Alternatively,

optical-electric means, such as radiation pyrometers may be used. Sincethe flame front contains an appreciable concentration of organicradicals and ions, its position may also be detected by ion sensitivemeans such as a capacitor in the tank circuit of a high frequencyoscillator where-by linear displacement of the flame will change thedielectric constant of the capacitor and hence, the resonancecharacteristic of the oscillator. Or the llame region may comprise adirect-current ionization gap. Those skilled in the art may readilydetermine the appropriate sensing means for determining the position ofthe stabilized cool flame in the combustion zone of the presentinvention.

In a preferred embodiment of the inventive apparatus, the cool flamefront for the combustible fluid sample is positioned between a pair ofthermocouples 4 and 5 placed in the combustion zone. Both thermocoupleswill be at about the same temperature and the voltage appearing at theinput of the differential temperature controller 12 will beapproximately zero. However, equally satisfactory operation can beachieved by having a net voltage difference if the positive or negativecorresponding to a temperature differential is in the order of F. to 40F. This means that the flame front in the combustion chamber 2 is thenslightly asymmetrical with respect to the thermocouples 4 and 5. Whilethis mode achieves greater sensitivity, it is not a critical requirementand one may still get good results with the apparatus if a zerotemperature differential is maintained within the device 12..

In any event, the sensing means 4 and 5, the transmitting means 10 and11, and the differential temperature controller '12 will enable one todetermine the exact position of the cool flame front by a differentialtemperature measurement. Controller 12 will then activate the pressurecontrol means 14 in order to adjust the flame front to a position wherethere is, as previously mentioned, typically a zero temperaturedifferential. Therefore, the change in combustion pressure which isrequired to immobilize the llame front in its predetermined location, isa correlatable function with the composition of the fuel which is beingoxidized within the combustion chamber 2.

Accordingly, then, there is provided within the apparatus a pressuresensing means 15 which develops a continuous pressure signal transmittedvia line 16 to a transducer 17. The transducer 17 converts the pneumaticor mechanical pressure signal 16 into an electrical signal which may bea voltage signal or an amperage signal. The transducer I17 transmits aconverted parameter output signal via line L18 into a signalconditioning means 25, which in this embodiment comprises a digital oran analog computer means. Computer means 25 contains an internalcomputer program by which the converted parameter signal 18 iscontinuously converted into an output signal 26` which is functionallyrepresentative of and correlatable with the octane rating of thecombustible gasoline fuel introduced into the system via line 19. Thecondition output signal 26 is thereupon transmitted to an octane displaydevice 27 which may comprise a recording chart device, or a tapeprint-out device, or any other type of indicating means. In addition,the octane display device 27 may comprise a control system whereby anoutput signal for control of octane number is transmitted to means notshown for controlling the octaine rating of the fluid which provides thetest sample entering via line 19.

As previously noted, the apparatus of the present invention is typicallylocated out-of-doors. Accordingly, it is subject to combustion effectscreated by changes in atmospheric conditionsuln order to compensate forchanging atmospheric conditions, there is provided Within the apparatusof the present invention a temperature sensing means 28 which is capableof sensing any fluctuations in temperature within the elevatedtemperature zone 3. Alternatively, temperature sensing means 28 may bepositioned within combustion chamber 2 in order to sense actualfluctuations in induction section temperature. Temperature sensing means28 passes a temperature output signal via transmitting means 29 to thesignal conditioning means 25. The internal program of the computer means25 thereupon makes a temperature correction to the condition outputsignal passing via line 26, whereby the octane value thereafterindicated by octane display device 27 is continuously compensated forany error in the indicated composition characteristic which is due totemperature fluctuations in the induction section of chamber 2 or in theelevated temperature zone 3, caused by changes in atmosphericconditions.

In addition, the apparatus of the present invention provides for arecalibration or a re-zoning of the system for deviations created byother combustion effects which are not reflective of the compositioncharacteristic of the fuel being tested. Accordingly, there is providedmeans for periodically passing into the combustion chamber 2 a referencefuel by which the system may be recalibrated.

Thus, there is shown in FIG. l a reference fuel passing into the systemvia line 20. A timing device 23 passes a timing signal via line 22 intoa control valve 21. During the period of isolation, the control valve 21receives a timing signal by which the test sample of line 19 is switchedout of the system and the reference fuel of line 20 is switched into thesystem. Thereafter, during the isolation or reference period, referencefuel passes via line 7 into line 6 in admixture with the air enteringvia. line 8.

The reference fuel produces a stabilized cool flame which is indicativeof the octane rating, or other composition characteristic beingdetermined, of the reference fuel. The temperature sensing means 4 and 5transmit the sensed temperature signals via means `10 and 11 into thedifferential temperature controller 12, whereupon differentialtemperature controller 12 passes a control signal via line 13 topressure control means 14. The pressure sensing means 15 passes thepressure signal via line 16 into transducer 17 which in turn passes aconverted parameter signal 18 into the computer means 25. The internalprogram of computer means 25 compares the signal |18 with a referencesignal contained within the program. The reference signal is indicativeof the known actual octane rating of the reference fuel. rl`he timingdevice 23 sends a signal via line 24 to the computer means 25 duringthose periods of time when the reference fuel is being burned withincombustion chamber 2l.

Accordingly then, the computer program will make a compensatingadjustment to the condition output signal 26 in order to eliminate anydeviation of converted parameter signal 18 from the known signal whichis reflective of the actual composition characteristic or octane numberof the reference fuel. When the period of isolation is ended, timer 23sends a signal via line 22 to valve 21 to swing the valve in a mannersufficient to isolate the reference fuel of line from the system and tocontinue the introduction of test sample via line 19. At this pointthen, the timing signal passing via line 24 to computer means 25,informs the computer means that the reference fuel has been cut out ofthe system and that the test sample has been reintroduced. The internalcomputer program of the computer means 25 at this point retains anyreference fuel correction which was made within the system.Consequently, the resulting condition output signal passing via line 26to octane display device 27 when the test sample is being tested, willreliect a compensation or recalibration of the system for the referencefuel.

Accordingly, then, the indicated octane number of the test sample willhave been corrected for temperature conditions and for other combustionconditions which were not truly indicative of composition characteristicor octane number and, therefore, the indicated condition output signal26 will be truly indicative of and directly correlatable with the octanenumber or other composition characteristic of the test sample beingoxidized in combustion chamber 2.

Referring now to FIG. 2, there is shown a second ernbodiment of thepresent invention wherein the signal conditioning means of FIG. 1, thecomputer means 25, and its internally contained program is replaced by asignal conditioning means preferably comprising a network of analogelements, although a network of digital elements may be used.

The basic elements of the analytical apparatus, which are disclosed inFIG. l, are again illustrated in FIG. 2. However, the transducer outputsignal leaving transducer 17 is transmitted via means 18 into a signalconditioning network 30. The signaling conditioning network 30` is atype of apparatus which is lwell known in the art. The convertedparameter signal 18 passing from transducer 17 has a fixed correlationbetween the pressure which is sensed in the combustion chamber 2 by thepressure sensing means 15, and the resulting electrical output signalwhich is passed through the signaling conditioning network. Theconditioning network 30` either multiplies, or it adds and substracts tothe received transducer signal 18 in order to produce a net outputsignal which is correlatable `with octane rating or any othercomposition characteristic being determined. In the preferredembodiment, signal conditioning network 30 will add and subtract to thesignal 18. The resulting pressure output signal is transmitted fromsignal conditioning network 3l)` via transmitting means 31 into asumming means 32.

In addition, in the embodiment illustrated in FIG. 2, the temperaturesignal which is sensed in the elevated temperature zone 3 by the sensingmeans 28 is transmitted via line 29 into a signal conditioning network33. Again, the signal conditioning network 33 is a type of network whichis well known in the art. The temperature signal has a fixed correlationbetween the temperature in the elevated temperature zone 3 and theoctane rating or other composition characteristic being determinedwithin the combustion chamber 2. 'Ihe conditioning network 33,therefore, adds or subtracts to the signal 29 in a manner sufficient tocompensate for any temperature deviations from a fixed temperature whichis the standard base ternperature for the elevated temperature zone 3.Alternatively, induction section temperature may be sensed by means 28,and network 33 may compensate for any deviations from the base inductionsection temperature. The resulting signal is passed from the signalconditioning network 33 with a compensation for any temperaturedeviation, into summing means 32 via transmitting means 34.

Summing means 32 receiving the temperature signal 34 and the pressureoutput signal 31, thereupon algebraically sums the two signals. The netresult of the algebraic summation accomplished by summing means 32 is amodified parameter signal which is, in fact, the net output signal whichis indicative of the apparent composition characteristic as compensatedfor any temperature fluctuations. Thus, when the test sample of line 19is oxidized in combustion chamber 2, the summing means 32 sends acondition output signal 26 to the octane display device 27 which givesthe apparent octane rating ofthe test sample.

When reference fuel is being oxidized in chamber 2, summing means 32sends a condition output signal via transmitting means 35 to an erroramplifier 36, as well as the condition output signal 26 to the displaydevice 27. The error amplifier 36 is a device which is well known in theart. The error amplifier contains a manual setpoint which isrepresentative of the actual known octane number of the reference fuel.Accordingly, the error amplifier receives the timing signal from timer23 via transmitting means 24 when the reference fuel is Ibeing oxdizedWithin the combustion chamber 2. At this point then, the error amplifiercompares the condition output signal 35 with the known setpoint which iscorrelatable with the kno-wn actual composition characteristic, such asoctane number, of the reference fuel. Thereupon the error amplifierdevelops an output signal which is a function of the difference betweenthe setpoint and the actual summation or condition output signal 35.

The error amplifier 36 transmits its output signal via transmittingmeans 37 to a servo amplifier 38. The servo amplifier is a device whichis well known in the art. The servo amplifier upon receiving the erroramplifier output signal, responds to the error output signal in order tomake a correction to bring the condition output signal 3S into balancewith the setpoint contained within the error amplifier. Accordingly, theservo amplifier 38 develops an output signal which is proportional tothe error amplifier output signal which has been received. The servoamplifier is a power amplier sending a power signal via means 39 to aservo-motor located within signal conditioning network 30. Theservo-motor mechanically adjusts the signal conditioning network 30 toproduce an ultimate summation or condition output signal 35 which isidentical to the manual setpoint which is contained in the erroramplifier 36. Thus the system is corrected to the known oct-ane value orother base line composition characteristic of the reference fuel. A

The resulting pressure output signal transmitted via line 31 thereuponbecomes directly correlatable with the octane number or other measuredcomposition characteristic of the reference fuel being oxidized withincombustion chamber 2. Summing means 32 thereupon develops an outputsignal 35 which passes to the error amplifier and is therein indicatedto be in balance with the manual setpoint. At this juncture then, themodified condition output signal which is transmitted via means 2-6 tothe octane display device 27 will indicate the true octane number forthe reference fuel as corrected for combustion effects which are notindicative of the composition characteristic 'being determined.

When the system reaches a time when the period of isolation is over,timer 23 will switch valve 21 by means of a signal passing via line 22in order to cut out the reference fuel 20 and reintroduce the testsample 19 into the analyzer of the present invention. At this pointthen, the timer 23 sends a signal via transmitting means 24 to the erroramplifier which will enable the system to hold the compensatingadjustment which was made in signal conditioning network 30 to balanceout the reference fuel output signal 35 with the manual setpoint. Inthis manner then, when the test sample of line 19` is being oxidized themodified condition output signal 26 passing to the display device 27 isindicative of the composition characteristic being measured, such asoctane number, while being compensated for temperature fiuctuation andfor any deviations of the reference fuel signal from the known basereference signal.

PREFERRED EMBODIMENTS Those skilled in the art will readily preceive theapparatus configuration of the present invention and the 15 method ofoperation which have been disclosed hereinabove. Additionally, thoseskilled in the art can readily preceive the advantages of the presentinvention as disclosed hereinabove.

However, even though those skilled in the art will easily recognize thedistinction between the terms signal conditioning means and signalconditioning network, it is deemed advantageous to dene and distinguishthese terms as used herein, Referring to FIG. 1, the signal conditioningmeans comprises the computer means 25, which contains an internalcomputer program for making compensating adjustments to produce thecorrected condition output signal. Referring to FIG. 2, the signalconditioning means comprises the network of elements 30 through 39,which is, in fact, a computing system for making the compensatingadjustments. Thus, the signal conditioning networks 30 and 33 which aredisclosed in FIG. 2, are individual elements contained within the signalconditioning means of that embodiment.

Furthermore, it is to be noted that the composition characteristic beingdetermined by the present invention, typically octane rating, isindicated by a condition output signal which is a function of andcorrelatable with the composition characteristic being determined.However, those skilled in the art will realize that the condition outputsignal, as illustrated by the elements 26 and 35, is in fact a modifiedparameter output signal which in the preferred embodiment is a pressuresignal. Thus, when the reference fuel is passing to the combustionchamber 2 and condition output signal 35 is compared with the referencevalue signal in error amplifier 36, the reference value signal is, infact, being matched with a modified parameter signal 35.

Therefore, from the above description it may now be summarized that onepreferred embodiment of the present invention provides a method fordetecting composition characteristic of a combustible fluid whichcomprises. (a) introducing a sample stream of said fluid and a stream ofoxygen-containing gas into one end of a combustion zone encompassed by azone of elevated temperature, said combustion zone including aninduction section maintained at elevated temperature; (b) partiallyoxidizing said sample stream in said combustion zone under conditionssufficient to generate and maintain therein, a cool flamecharacteristized by a relatively narrow well-defined llame front spacedfrom said one end; (c) sensing the position of said flame front relativeto said one end, and developing therefrom a control signal; (d)utilizing said control signal to adjust a combustion parameter selectedfrom the group consisting of combustion zone pressure, induction sectiontemperature, sample stream flow rate, and oxygen-containing gas streamflow rate, in a manner sullicient to immobilize said flame frontrelative to said one end regardless of fluctuations in the compositioncharacteristic of said sample stream; (e) sensing the adjusted parameterand passing a first parameter signal into signal conditioning means; (f)manipulating said yfirst parameter signal in said signal conditioningmeans and therefrom producing a first condition output signalfunctionally representative of the apparent composition characteristicof said fluid sample stream, and functionally responsive to changes incomposition characteristic of said sample stream; g) periodicallyisolating said sample stream from said combustion zone, andsimultaneously passing a stream of reference fuel having a known valueof composition characteristic, into siad zone in a manner sufficient tocontinue the generation of said immobilized llame front; (h) sensing theadjusted parameter during the period of isolation and passing a secondparameter signal into said signal conditioning means, said secondparameter signal being functionally representative of the apparentcomposition characteristic of said reference fuel; (i) comparing saidsecond parameter signal with a reference value of parameter signalfunctionally corresponding to the actual known value of compositioncharacteristic of said reference fuel; (j) adjusting said signalconditioning means in a manner sufficient to produce a second conditionoutput signal which is compensated to reflect the elimination of thedifference between said second parameter signal and said reference valueparameter signal, and which is thereby functionally representative ofthe actual known composition characteristic of said reference fuel; (k)periodically isolating said reference fuel stream from said combustionzone while retaining the signal conditioning adjustment of step (j), andsimultaneously passing said lluid sample stream into said zone in amanner sufficient to maintain said llame front, whereby said signalconditioning means receives a third parameter signal and therefromdevelops a third condition output signal compensated for the deviationof said second parameter signal from said reference value parametersignal, and said third condition output signal is thereby functionallyrepresentative of the apparent composition characteristic of said samplestream as adjusted for reference fuel deviation; (l) sensing atemperature selected from the group consisting of a temperature in saidinduction section and a temperature in said elevated temperature zone,andy passing a signal representative of sensed temperature into saidsignal conditioning means; (m) adjusting said signal conditioning meansresponsive to said sensed temperature signal, whereby said signalconditioning means develops a modified third condition output signalcompensated for combustion effects not indicative of compositioncharacteristic, and said modified third condition output signal isthereby functionally representative of the actual compositioncharacteristic of said sample stream.

In addition, from the above description it may be further summarizedthat a preferred embodiment of the present invention is a compositionanalyzer for detecting a composition characteristic of a combustiblechemical iluid which comprises in combination: (a) a combustion chamberencompassed by an outer chamber confining a zone of elevated temperaturethereinbetween, said combustion chamber including an induction sectionmaintained at elevated temperature; (b) means for generating Within saidcombustion chamber, a cool flame characterized by a relatively narrowwell-dened flame front, utilizing as fuel therefor said combustiblechemical lluid to be analyzed, said generating means including meanspassing a stream of said fluid and a stream of oxidizer into saidcombustion chamber; (c) means sensing the physical position of saidllame front within said combustion chamber; (d) control means coupled tosaid position sensing means, and adapted to adjust a combustionparameter selected from the group consisting of combustion presure,induction section temperature, liuid stream flow rate, and oxidizerstream ilow rate in a manner sullicient to immobilize said flame frontin a constant physical position relative to said combustion chamber; (e)means sensing the adjusted parameter and developing a parameter outputsignal which is functionally representative of the compstioncharacteristic of said fluid stream; (f) signal conditioning meansreceiving said parameter output signal; (g) condition signal generatingmeans within said signal conditioning means producing a condition outputsignal representative of said composition characteristics; (h) meansperiodically isolating said lluid stream from said llame generatingmeans, and for simultaneously passing a stream of reference fuel havinga known value of composition characteristic, into said llame generatingmeans in a manner suflicient to continue the generation of saidimmobilized flame front; (i) means passing to said signal conditioningmeans, a timing signal indicative of the passage of reference fuel tosaid flame generating means; (j) comparison means within said signalconditioning means, responsive to said timing signal, adapted to comparethe condition output signal generated due to reference fuel llame frontwith a reference value signal functionally corresponding to the actualknown value of composition characteristic of said reference fuel,' andtherefrom developing a comparison signal; (k) adjusting means withinsaid signal conditioning means, responsive to said comparison signal,and adapted to adjust said condition signal generating means tocompensate for deviation between the condition output signal generateddue to reference fuel flame front and said reference value signal; (l)means for retaining said adjustment to said condition signal ygeneratingmeans when said isolation period is ended and said uid stream isreturned to said flame generating means in place of said reference fuel,whereby the condition output signal generated by said uid stream flamefront is compensated for deviation between the parameter signalgenerated due to the reference fuel flame front and said reference valueof parameter signal; (m) means sensing a temperature selected from thegroup consisting of a temperature within said induction section and atemperature within said conned elevated temperature zone, and developinga temperature signal responsive to fluctuations in sensed temperature;(n) means transmitting said sensed temperature signal to said signalconditioning means; and (o) means within said signal conditioning means,modifying said condition output signal generated by said fluid streamllame front responsive to fluctuations in said sensed temperature andthereby compensating saidcondition output signal for combustion effectsnot indicative of composition characteristic, thereby resulting in acondition output signal functionally representative of and correlatablewith the composition characteristic of said combustible chemical fluid.

The invention claimed:

1. Method for detecting composition characteristic of a combustiblefluid which comprises:

(a) introducing a sample stream of said tiuid and a stream ofoxygen-containing gas into one end of a combustion zone including aninduction section maintained at elevated temperature;

(b) partially oxidizing said sample stream in said combustion zone underconditions suicient to generate and maintain therein, a cool llamecharacterized by a relatively narrow well-defined flame front spacedfrom said one end;

(c) sensing the position of said llame front relative to said one end,and developing therefrom a control signal;

(d) utilizing said control signal to adjust a combustion parameterselected from the group consisting of combustion zone pressure,induction section temperature, sample stream flow rate, andoxygen-containing gas stream flow rate, in a manner suicient toimmobilize said flame front relative to said one end regardless offluctuations in the composition characteristic of said sample stream;

(e) sensing the adjusted parameter and passing a first parameter signalinto signal conditioning means;

(f) manipulating said first parameter signal in said signal conditioningmeans and therefrom producting a irst condition output signalfunctionally representative of the apparent composition characteristicof said fluid sample stream, and functionally responsive to changes incomposition characteristic of said sample stream;

(g) periodically isolating said sample stream from said combustion zone,and simultaneously passing a stream of reference fuel having a knownvalue of composition characteristic, into said zone in a mannerSullicient to continue the generation of said immobilized llame front;

(h) sensing the adjusted parameter during the period of isolation andpassing a second parameter signal into said signal conditioning means,said second parameter signal being functionally representative of theapparent composition characteristic of said reference fuel;

(i) comparing said second parameter signal with a reference value ofparameter signal functionally corresponding to the actual known value ofcomposition characteristic of said reference fuel;

(j) adjusting said signal conditioning means in a manner suicient toproduce a second condition output signal which is compensated to recctthe elimination of the difference between said second parameter signaland said reference value parameter signal, and which is therebyfunctionally representative of the actual known compositioncharacteristic of said reference fuel; and,

(k) periodically isolating said reference fuel stream from saidcombustion zone while retaining the signal conditioning adjustment ofstep (j), and simultaneously passing said fluid sample stream into saidzone in a manner sufficient to maintain said flame front, whereby saidsignal conditioning means receive a third parameter signal and therefromdevelops a third condition output signal compensated for combustioneffects not indicative of composition charcteristic, and said thirdcondition output signal is thereby functionally representative of theactual composition characteristic of said sample stream.

2. Method of claim 1 wherein said combustible lluid comprises at leastone gasoline boiling range hydrocarbon, and said reference fuelcomprises at least one gasoline boiling range hydrocarbon.

3. Method of claim 2 wherein said adjusted combustion parameter iscombustion zone pressure.

4. Method of claim 2 wherein said composition characteristic is octanerating.

5. Method for detecting composition characteristic of a combustiblefluid which comprises:

(a) introducing a sample stream of said fluid and a stream ofoxygen-containing gas into one end of a combustion zone encompassed by azone of elevated temperature, said combustion zone including aninduction section maintained at elevated temperature;

(b) partially oxidizing said sample stream in said combustion Zone underconditions sufficient to generate and maintain therein, a cool flamecharacterized by a relatively narrow well-defined flame front spacedfrom said one end;

(c) sensing the position of said llame front relative to said one end,and developing therefrom a control signal;

(d) utilizing said control signal to adjust a combustion parameterselected from the group consisting of combustion zone pressure,induction section temperature, sample stream ow rate, andoxygen-containing gas stream flow rate, in a manner suicient toimmobilize said flame front relative to said one end regardless offluctuations in the composition characteristic of said sample stream;

(e) sensing the adjusted parameter and passing a first parameter signalinto signal conditioning means; (f) manipulating said first parametersignal in said signal conditioning means and therefrom producing a rstcondition output signal functionally representative of the apparentcomposition characteristic of said fluid sample stream, and functionallyresponsive to changes in composition characteristic of said samplestream;

(g) periodically isolating said sample stream from said combustion zone,and simultaneously passing a stream of reference fuel having a knownvalue of composition characteristic, into said zone in a mannersufficient to continue the generation of said immobilized ame front;

(h) sensing the adjusted parameter during the period of isolation andpassing a second parameter signal into said signal conditioning means,said second parameter signal being functionally representative of theapparent composition characteristic of said reference fuel;

(i) comparing said second parameter signal with a reference value ofparameter signal functionally corresponding to the actual known value ofcomposition characteristic of said reference fuel;

(j) adjusting said signal conditioning means in a manv ner suilicient toproduce a second condition output signal which is compensated to reflectthe elimination of the difference between said second parameter signaland said reference value parameter signal, and which is therebyfunctionally representative of the actual known compositioncharacteristic of said reference fuel;

(k) periodically isolating said reference fuel stream from saidcombustion Zone while retaining the signal conditioning adjustment ofstep (j), and simultaneously passing said iluid sample stream into saidzone in a manner suiiicient to maintain said flame front, whereby saidsignal conditioning means receives a third parameter signal andtherefrom develops a third condition output signal compensated `for thedeviation of said second parameter signal from said reference valueparameter signal, and said third condition output signal is therebyfunctionally representative of the apparent composition characteristicof said sample stream as adjusted for reference fuel deviation;

(l) sensing a temperature selected from the group consisting of atemperature in said induction section and a temperature in said elevatedtemperature zone, and passing a signal representative of sensedtemperature into said signal conditioning means;

(m) adjusting said signal conditioning means responsive to said sensedtemperature signal, whereby said signal conditioning means develops amodified third condition output signal compensated for combustioneffects not indicative of composition characteristic, and said modiedthird condition output signal is thereby functionally representative ofthe actual composition characteristic of said sample stream.

6. Method of claim wherein said temperature in the elevated temperaturezone is continuously sensed, said sensed temperature signal iscontinuously passed into said signal conditioning means, and said signalconditioning means is continuously adjusted responsive to said sensedtemperature signal, whereby said rst, second and third condition outputsignals are continuously modied to compensate for temperaturefluctuation in said elevated temperature zone.

7. Method of claim 6 wherein Said combustible uid comprises at least onegasoline boiling range hydrocarbon, and said reference fuel comprises atleast one gasoline boiling range hydrocarbon.

8. Method of claim 7 wherein said adjusted combustion .parameter iscombustion zone pressure.

9. Method of claim 7 wherein said composition characteristic is octanerating.

10. Method of claim 5 wherein said combustible fluid comprises at leastone gasoline boiling range hydrocarbon, and said reference fuelcomprises at least one gasoline boling range hydrocarbon.

11. Method of claim 10 wherein said adjusted combustion parameter iscombustion zone pressure.

12. Method of claim 10 wherein said composition characteristic is octanerating.

13. Method for detacting composition characteristic of a combustiblefluid which comprises:

(a) introducing a sample stream of said -uid and a stream ofoxygen-containing Igas into one end of a combustion zone encompassed bya zone of elevated temperature, said combustion zone including aninduction section maintained at elvated temperature;

(b) partially oxidizing said sample stream in said combustion zone underconditions sucient to generate and maintain therein, a cool llamecharacterized by a relatively narrow Well-dened flame front spaced fromsaid one end;

(c) sensing the position of said llame front relative to said one end,and developing therefrom a control signal;

(d) utilizing said control signal to adjust a combustion parameterselected from the group consisting of combustion zone pressure,induction section temperature, sample stream flow rate, andoxygne-containing gas stream flow rate, in a manner sufficient toimmobilize said flame front relative to said one end regardless offluctuations in the composition characteristic of said sample stream;

(e) sensing the adjusted parameter and developing a parameter signalresponsive to changes in said composition characteristic;

(f) sensing a temperature selected from the group consisting ofinduction section temperature and a temperature of said elevatedtemperature zone, and developing a temperature signal responsive touctuations in sensed temperature;

(g) passing said parameter signal and said temperature signal intosignal conditioning means, and producing therefrom a lcondition outputsignal functionally representative of the composition characteristic ofsaid fluid sample stream, said condition output signal being indicativeof said composition characteristic as corrected for fluctuations insensed temperature.

14. Method of claim 13 wherein said combustible tluid comprises at leastone gasoline boiling range hydrocarbon.

15. Method of claim 14 wherein said adjusted combustion parameter iscombustion zone pressure.

16. Method of claim 14 wherein said composition characteristic is octanerating.

17. A composition analyzer for detecing a composition characteristic ofa combustible chemical iluid which comprises in combination:

(a) a combustion chamber, including an induction section;

(b) means for generating within said combustion chamber, a cool flamecharacterized by a relatively narrow well-dened flame front, utilizingas fuel therefor said combustible chemical fluid to be analyzed, saidgenerating means including means passing a stream of said fluid and astream of oxidizer into said combustion chamber;

(c) means sensing the physical position of said flame front within saidcombustion chamber;

(d) control means coupled to said position sensing means, and adapted toadjust a combustion parameter selected from the Igroup consisting ofcombustion pressure, induction section temperature, iluid stream ilowrate, and oxidizer stream ow rate, in a manner sufficient to immobilizesaid flame front in a constant physical position relative to saidcombustion chamber;

(e) means sensing the adjusted parameter and developing a parameteroutput signal which is functionally representative of the compositioncharacteristic of said uid stream;

(f) signal conditioning means receiving said parameter output signal;

(g) condition signal generating means within said signal conditioningmeans, producing a condition output signal functionally represntative ofsaid composition characteristic;

(h) means periodically isolating said lluid stream from said flamegenerating means, and simultaneously passing a stream of reference fuelhaving a known value of composition characteristic, into said flamegenerating means in a manner suicient to continue the generation of saidimmobilized flame front;

(i) means passing to said signal conditioning means, a timing signalindicative of the passage of reference fuel to said llame generatingmeans;

means, responsive to said timing signal, adapted to compare thecondition output signal generated due to reference fuel flame front witha reference value signal fuctionally corresponding to the actual knownvalue of composition characteristic of said reference fuel, andtherefrom developing a comparison signal;

(k) adjusting means within said signal conditioning means, responsive tosaid comparison signal, and adapted to adjust said condition signalgenerating means to compensate for reviation between the conditionoutput signal generated due to reference fuel flame front and saidreference value signal; and

(l) means for retaining said adjustment to said condition signalgenerating means when said isolation period is ended and said fluidstream is returned to said flame generating means in place of saidreference fuel, whereby the condition output signal generated by saidfluid stream flame front is compensated for combustion effects notindicative of composition characteristic, and said condition outputsignal is thereby functionally representative of and correlatable withthe actual composition characteristic of said combustible chemicalfluid.

18. Apparatus of claim 17 wherein said signal conditioning meanscomprises computer means.

19. Apparatus of claim 17 wherein said flame position sensing meanscomprises a pair of axially spaced temperature sensing elements.

20. A composition analyzer for detecting a composition characteristic ofa combustible chemical fluid which comprises in combination:

(a) a combustion chamber encompassed by an outer chamber confining azone of elevated temperature thereinbetween, said combustion chamberincluding an induction section maintained at elevated temperature;

(b) means for generating within said combustion chamber, a cool flamecharacterized by a relatively narrow well-defined flame front, utilizingas fuel therefor said combustible chemical fluid to be analyzed, saidgenerating means including means passing a stream of said fluid and astream of oxidizer into said combustion chamber;

(c) means sensing the physical position of said flame front within saidcombustion chamber;

(d) control means coupled to said position sensing means, and adapted toadjust a combustion parameter selected from the group consisting ofcombustion pressure, induction section temperature, iluid stream flowrate, and oxidizer stream flow rate, in a manner sufficient toimmobilize said `flame front in a constant physical position relative tosaid combustion chamber;

(e) means sensing the adjusted parameter and developing a parameteroutput signal which is functionally representative of the compositioncharacteristic of said fluid stream;

(f) means sensing a temperature selected from the group consisting of atemperature within said induction section and a temperature of saidconfined elevated temperature zone, and developing a temperature signalresponsive to fluctuations in sensed temperature; and,

(g) signal conditioning means receiving said parameter output signal andsaid sensed temperature signal, and producing therefrom a conditionoutput signal which is functionally representative of and correlatablewith said composition characteristic of the combustible chemical fluid,said condition output signal being indicative of said compositioncharacteristic as corrected for fluctuations in sensed temperature.

21. Apparatus of claim 20 wherein said signal conditioning meanscomprises computer means.

22 22. Apparatus of claim 20 wherein said flame position sensing meanscomprises a pair of axially spaced temperature sensing elements.

23. A composition analyzer for detecting a composition characteristic ofa combustible chemical fluid which comprises in combination:

(a) a combustion chamber encompassed by an outer chamber confining azone of elevated temperature thereinbetween, said combustion chamberincluding an induction section maintained at elevated ternperature;

(b) means for generating within said combustion chamber, a cool flamecharacterized by a relatively narrow well-defined flame front, utilizingas fuel therefor said combustible chemical fluid to be analyzed, saidgenerating means including means passing a stream of said fluid and astream of oxidizer into said combustion chamber;

(c) means sensing the physical position of said flame front within saidcombustion chamber;

(d) control means coupled to said position sensing means, and adapted toadjust a combustion parameter selected from the group consisting ofcombustion pressure, induction section temperature, fluid stream flowrate, and oxidizer stream flow rate, in a manner sufficient toimmobilize said flame front in a constant physical position relative tosaid combustion chamber;

(e) means sensing the adjusted parameter and developing a parameterOutput signal which is functionally representative of the compositioncharacteristic of said fluid stream;

(f) signal conditioning means receiving said parameter output signal;

(g) condition signal generating means within said signal conditioningmeans, producing a condition output signal functionally Irepresentativeof said composition characteristic;

(h) means periodically isolating said fluid stream from said llamegenerating means, and simultaneously passing a stream of reference fuelhaving a known value of composition characteristic, into said llamegenerating means in a manner sufficient to continue the generation ofsaid immobilized llame front;

(i) means passing to said signal conditioning means, a timing signalindicative of the passage of reference fuel to said flame generatingmeans;

(j) comparison means within said signal conditioning means, responsiveto said timing signal, adapted to compare the condition output signalgenerated due to reference fuel flame front with a reference valuesignal functionally corresponding to the actual known value ofcomposition characteristic of said reference fuel, and therefromdeveloping a comparison signal;

y(k) adjusting means within said signal conditioning means, responsiveto said comparison signal, and adapted to adjust said condition signalgenerating means to compensate for deviation between the conditionoutput signal generated due to reference fuel flame front and saidreference value signal;

(l) means for retaining said adjustment to said condition signalgenerating means when said isolation period is ended and said fluidstream is returned to said flame generating means in place of saidreference fuel, whereby the condition output signal generated by saidfluid stream flame front is compensated for deviation between thecondition output signal generated due to the reference fuel flame frontand said reference value signal;

(m) means sensing a temperature selected from the group consisting of atemperature within said induction section and a temperature within saidconfined elevated temperature zone, and developing a temperature signalresponsive to fluctuations in sensed temperature;

(n) means transmitting said sensed temperature signal 25.` Apparatus ofclaim 23 wherein saidwame position to said signal conditioning means;and, sensing means comprises a pair of axially spaced tempera- (o) meanswithin said signal conditioning means, iure Sensing elementsmodifyingsaid condition output signal generated by said iluid stream ame frontresponsive to iluctuations 5 References Cited in said sensed temperatureand thereby compensating UNITED STATES PATENTS said condition outputsignal for combustion effects 3,463,613 8/1969 Penske et a1. 23 254 notindicative of composition characteristic, thereby 3,533,746 10/1970Penske 23 230 resulting in a condition output signal functionally hrepresentative of and correlatable with the com- 10 MORRIS O- WOLKPrimary EXamlnef position characteristic of said combustible chemical R.E. SERWIN, Assistant Examiner fluid. 24. Apparatus of claim 23 whereinsaid signal con- U-S C1' X'R ditioning means comprises computer means.15 23-232, 253, 254; 73--35; 208-17; 43175

